As a fastener element which is conventionally used for a slide fastener, a fastener element made of synthetic resin which is formed individually by injection-molding synthetic resin onto a fastener tape, a continuous fastener element which is formed by molding a mono-filament in a coiled shape or a zigzag shape, and a metallic fastener element which is formed by caulking an approximately Y-shaped metallic element material onto a fastener tape, and the like are known.
Further, in general, the fastener element made of synthetic resin is directly fixed to the fastener tape when injection molding. Therefore, by broadening a fixing area of the fastener element with respect to the fastener tape, fixing strength of the fastener element with respect to the fastener tape can be enhanced. For this reason, in a conventional fastener element made of synthetic resin, an element width dimension of each fastener element has been set large in order to ensure the fixing strength of the fastener element stably.
Whereas, since the metallic fastener element is attached to the fastener tape, for example by caulking an element which has an approximately-Y-shaped cross section, the metallic fastener element can easily obtain enough fixing strength without setting the element width dimension as large as in the fastener element made of synthetic resin as described above.
Also, for example, WO 2010-082294 A (Patent Document 1) and WO 2013-051149 A (Patent Document 2) disclose fastener stringers in which the appearance quality of the fastener element is enhanced. Those fastener elements are formed with lighter synthetic resin compared to a metal and have an appearance (show) like a metallic fastener element.
For example, the fastener element of the fastener stringer described in Patent Document 1 is attached to a tape side edge portion of a fastener tape by injection-molding thermoplastic resin. Each of the fastener elements has a first half portion disposed on the tape upper surface side of the fastener tape and a second half portion disposed on the tape lower surface side and formed integrally with the first half portion.
Further, here, an upper and lower direction refers to a tape front and back direction which is orthogonal to a tape surface of the fastener tape. Also, a top and bottom direction refers to a length direction of the fastener tape, and a left and right direction refers to a tape width direction of the fastener tape.
In this fastener element of Patent Document 1, the first half portion includes a fixing portion fixed to the fastener tape and an extending portion extending tape outward direction from the fixing portion. The extending portion has a tapering shape in which an element width dimension in a tape length direction gradually decreases toward a tip end portion of the extending portion.
Further, in the first half portion, in order to ensure the fixing strength with the fastener tape, the element width dimension in a lower end portion (end portion on a side which is in contact with the fastener tape) of the fixing portion has a predetermined size. In addition, a top side surface and a bottom side surface of the fixing portion in the first half portion are formed as a convex surface, which curves outward in a convex shape such that the element width dimension (longitudinal direction) of the first half portion gradually decreases from a tape surface of the fastener tape toward an upper surface of the fastener element.
The second half portion includes a body portion fixed to the fastener tape, a neck portion extending tape outward direction from the body portion and is constricted so as to decrease the dimension in the element width direction, and an coupling head portion extending further tape outward direction from the neck portion. Therefore, each fastener element in Patent Document 1 is coupled with a fastener element of a coupling counterpart on the side of the second half portion.
Since such a fastener element in Patent Document 1 is made of synthetic resin, it is light in weight compared to a metallic fastener element. Additionally, the fastener element is formed so as to appear thinner than a conventional fastener element made of synthetic resin by forming a convex surface on the first half portion, while ensuring fixing strength with the fastener tape, so that the fastener element has an appearance (show) like a metallic fastener element.
Therefore, a slide fastener to which the fastener elements in Patent Document 1 are attached looks stylish or adds a fashionable impression like a slide fastener in which metallic fastener elements are attached (simply mentioned “metal slide fastener” thereafter) and at the same time is significantly reduced in weight compared to a metal slide fastener.
However, for example, in a case that a slide fastener is formed using fastener stringers according to Patent Document 1 and a slider with a stopping mechanism having a stop claw portion which is capable of being engaged to a fastener element, the engagement of the stop claw portion in the slider of the fastener stringer in Patent Document 1 with the fastener element can be easily unstable since a convex surface is formed on the first half portion of the fastener element.
Furthermore, in the faster elements described in Patent Document 1, a shape of the first half portion formed on the tape upper surface side and a shape of the second half portion formed on the tape lower surface side differ from each other. Therefore, for example, in a slide fastener having fastener stringers described in Patent Document 1 and a separable bottom end stop, in a case that a so-called slide fastener for right-side insertion, in which an insert pin is inserted into a box from the right side of a box pin, and a so-called slide fastener for left-side insertion, in which the insert pin is inserted into the box from the left side of the box pin, are manufactured, dedicated dies for right-side insertion and for left-side insertion are required, respectively. This is one of the factors causing manufacturing cost increase of the slide fastener.
Meanwhile, Patent Document 2 discloses a fastener stringer in which a fastener element made of synthetic resin including a first half portion disposed on a tape upper surface side of a fastener tape, a second half portion disposed on a tape lower surface side of the fastener tape, and an element coupling portion disposed between the first and the second half portions.
In the fastener elements described in Patent Document 2, the first half portion (upper half portion) and the second half portion (lower half portion) have a plane-symmetrical shape each other about a center position in a tape front and back direction of the fastener tape. Therefore, here, the first half portion is described in detail, so that the detailed description of the second half portion is omitted.
The first half portion described in Patent Document 2 includes a first fixing portion fixed to the fastener tape and a first extending portion extending tape outward direction from the first fixing portion. The first extending portion has a tapered element shape in which an element width dimension gradually decreases toward a tip end portion. Further, atop side surface and a bottom side surface in the first half portion are formed to be a curved surface (concave surface), respectively, which curves in a concave shape such that the element width dimension gradually increases from an upper surface of the fastener element toward an upper tape surface of the fastener tape.
In the fastener elements described in Patent Document 2, the top side surface and the bottom side surface in the first half portion are formed as the concave surface respectively. Therefore, when the fastener element is viewed from an upper surface side, the top side surface and the bottom side surface in the first half portion can hardly be seen in comparison with a case that each of the side surfaces is formed in a convex shape, for example. In addition, reflecting light on the top side surface and the bottom side surface becomes hard to scatter toward upper side of the fastener element, so that a visual effect that the side surface on the top and the side surface on the bottom become to be shadow parts and appear dark, can be obtained.
Thus, in the fastener elements described in Patent Document 2, the first and the second half portions appear to be narrow in the element width direction and thin in an element length direction, so that it is possible to exhibit an appearance (show) closer to a metallic fastener element.
Further, in a case that a slide fastener is formed using fastener stringers according to Patent Document 2 and a slider with a stopping mechanism by a stop claw portion, since the top side surface and the bottom side surface in the first half portion of the fastener element are formed to be the concave surface in the fastener stringer of Patent Document 2, it is possible that the stop claw portion of the slider can be received and accommodated securely on the top side surface and the bottom side surface. Thereby, the engagement of the stop claw portion with respect to the fastener elements can be secured.
Furthermore, since the fastener elements described in Patent Document 2 have a plane-symmetrical shape about the center position in the tape front and back direction of the fastener tape, it is possible to be used for a slide fastener with right-side insertion and also with left-side insertion without altering the shape. Thereby, it can reduce the cost for molding dies for elements and the manufacturing cost reduction of the slide fastener can be achieved.
On the other hand, in Design Registration No. 1434591 (Patent Document 3), a fastener chain for slide fastener, in which fastener elements having substantially the same shape as those in Patent Document 2 are attached to a fastener tape, is illustrated.
Additionally, for example, in Design Registration No. 1434827 (Patent Document 4), a fastener chain for slide fastener which design is further improved by providing more irregularities on an upper surface of the fastener elements illustrated in Patent Document 2, is illustrated.